In recent years, small projectors have been actively developed which are capable of being easily carried and of projecting an image onto a large screen. For example, small projectors connectable to notebook personal computers and projector-incorporating video cameras have been already commercially available. Such a projector aligns laser beams emitted from multiple laser light sources onto one optical axis, and allows repeated scanning of the aligned laser beam in the horizontal direction and in the vertical direction, thereby projecting a desired image onto a screen.
Such a projector is also called a scanning image display apparatus, and is mounted on an automobile because of its easy increase in image brightness. In addition, application of such a projector to a head-up display that projects navigation information onto a windshield has been studied. When mounted on an automobile, the scanning image display apparatus (projector) is required to have performance that can withstand the temperature of a strict environment.
For example, the patent literature 1 discloses an example of a temperature compensation technique with respect to environment temperature, which is applied to an optical wavelength multiplex communication optical module. The optical module has, as its main component, a waveguide chip that is held to a predetermined temperature by a Peltier element, the waveguide chip and the Peltier element being covered by a thermal insulation material to be accommodated in a package. This allows the waveguide chip to be less susceptible to change in outside temperature. As a result, electric power supplied to the Peltier element for temperature control is reduced.
The Patent literature 2 discloses an example of a laser diode cooling technique using thermal shielding in a laser module having a laser diode used for a light source for optical communication signals. In the laser module, the laser diode as a heat source is mounted to a base that is temperature-controlled by a thermo-module (Peltier element), and is enclosed by a thermal shielding material that does not come into contact with an outside package. Thus, in this example, the flow of heat from the environment is reduced by the thermal shielding material. As a result, electric power supplied to the thermo-module for cooling the laser diode is reduced.